My issue is basically that the Skull Crack (SC) burst skill is a bad version of Earth Shaker (ES).
Both stun for the exact same time and both have identical recharges however ES is more powerful because it has alot more utility to it. ES has a big AoE so you can stun large groups, its also a targetable leap so you can use it as a closer or even a snare. To be blunt ES is incredibly strong, possibly even too strong and SC is quite mediocre in comparison.
It should be pointed out that main hand mace can be combined with an offhand where as hammer cannot so the stun can potentially be combined with many different skill setups, but even still SC seems rather lackluster when compared to the likes of Evicerate and Flurry.
I am by no means saying that SC is a terrible skill, 2 second stun is quite powerful. It just to me at least seems somewhat lacking (or maybe its just other bursts are OP idk.)